change some variable names to be more informative, add an image to error dialog

daemon/core/gui/dialogs/wlanconfig.py

@@ -27,13 +27,13 @@ class WlanConfigDialog(Dialog):
         self.canvas_node = canvas_node
         self.node = canvas_node.core_node
         self.config_frame = None
-        self.error = False
+        self.has_error = False
         try:
             self.config = self.app.core.get_wlan_config(self.node.id)
             self.draw()
         except grpc.RpcError as e:
             show_grpc_error(e, self.app, self.app)
-            self.error = True
+            self.has_error = True
             self.destroy()
 
     def draw(self):